Summer day camps (SDCs) represent a potential setting for the extension of health and wellness efforts targeting children during the school year. SDCs serve more than 14.3 million youth (<12yrs) annually and are the single largest organized setting, outside of the school year, where children can engage in healthy eating (i.e., consumption of fruits [F], vegetables [V], water [W] daily) and physical activity (PA). In 2011, th National Afterschool Association released childhood obesity policies referred to as the Healthy Eating and Physical Activity (HEPA) Standards, that call upon SDCs to ensure the children enrolled consume a serving of FV and W daily and engage in 60 minutes of moderate-to-vigorous PA (MVPA). From our extensive pilot work, we identified two areas SDCs' require support to meet the HEPA Standards. First, the majority of SDCs do not provide meals or snacks; rather, parents decide what types of foods are packed daily for their child to eat for lunch and snacks. To address this, we developed an innovative HE intervention for this setting - the Healthy Lunchbox Challenge (HLC) - grounded in Behavioral Choice Theory. The HLC is a low-cost weekly incentive program that awards points to children for packing healthy items for snacks/lunch (i.e., F, V, W). Second, we developed our innovative PA intervention approach (5 Ms and LET US Play) to address fundamental skills program leaders and staff require to facilitate PA. These focus on the LET US Play principles of removing lines and elimination, reducing team sizes, getting uninvolved staff/kids involved in activities, and using space, equipment, and rules effectively. Our long-term goal is to increase the number of SDCs that meet the HEPA Standards. The objective is to evaluate the effectiveness of a multi-component intervention designed to increase children's PA levels and improve the quality of foods/beverages children bring and consume in SDCs. The HEPA intervention uses a train-the-trainer model with SDC leaders to train their staff to deliver and integrate the intervention into routine practice. We will evaluate the HEPA intervention using a 4-year randomized controlled trial with 20 SDCs. An important feature of the study will be the evaluation of maintenance of the intervention after the removal of research support (e.g., training, boosters) during the final year as well as costs associated with implementation. Aim 1. Evaluate the impact of the HEPA interventions on: 1A: The proportion of children meeting the PA Standard (i.e., e60min MVPA/d) while attending summer day camp; 2A: The proportion of foods meeting the HE Standards (e.g., increase fruit, vegetable, water) children and staff bring and consume at the summer day camp; and 3A: Changes in children's age-sex specific BMI percentile from the start to end of summer. Aim 2: Evaluate the cost-effectiveness of the HEPA intervention; and Aim 3. Evaluate the maintenance of the HEPA intervention in summer day camps. The proposed study is significant because SDCs have the potential to reach millions of children. This research is innovative because no research has been conducted on this important setting and timeframe (summer vacation).